1. Field of the Invention
The invention relates to a device for swiveling objects, whereby the objects can essentially be tools or also a camera, having a greater swiveling region than is usual in the case of conventional technical solutions.
2. The Prior Art
It is known that tool swiveling devices are used in many areas of technology. If these devices swivel the tool tip about a fixed point, the tool tip remains stationary in the case of a change in orientation, and this can be desirable for many different reasons. Typical applications are found in robotics, as a robot wrist. A robot wrist is a device for changing the orientation of the tool guided by the robot, e.g. a drill or a milling device. A change in orientation of the tool does not require a change in the spatial position of the wrist. An increase in the size of the robot work space, an improvement in the positioning accuracy, and the possibility of a very rapid change in orientation are positive results of such a principle of effect.
In this connection, one must not overlook the fact that sufficient rigidity is often absent because of a greater number of elements for transferring force and for guidance. Such devices are also frequently impaired in their function by dirt, dust, and possible chips. These problems occur also in the case of devices with which cleaning work is carried out, for example using nozzles.
The following technical solutions, in which objects are swiveled about a fixed point, can be mentioned to characterize the state of the art:
An assembly for guiding minimally invasive surgical instruments is described according to EP 0556499 A2. For this purpose, the surgical instrument is to be swiveled about the puncture point in the body, about two axes that stand vertically on one another. This is accomplished, in the present document, by means of disposing two parallel crank mechanisms one behind the other. A plurality of elements, which are connected with one another with rotary articulation, form the connection between the tool—here, the surgical instrument—and the frame. The mechanical rigidity of this assembly is, of course, slight, because of the long chain of elements between frame and tool, and furthermore, the plurality of joints bears in it the risk of play. The great number of gear mechanism elements requires very precise production of each individual one, in order to achieve the desired movement behavior.
U.S. Pat. No. 5,697,939 A describes a similar solution. This document, too, uses a parallel crank—referred to as a parallelogram mechanism—for guidance and, in particular, fixation of a surgical instrument. Here, however, only one parallel crank mechanism is used, and swiveling is implemented about the axis that lies at a right angle to the swiveling axis of the parallel crank, with a rotary joint that lies close to the frame.
A solution that should also be mentioned in this connection is indicated in accordance with WO 03/086219 A2.
The aforementioned disadvantages are reduced with the two last references named, under some circumstances, but they continue to exist in the same manner.
In U.S. Pat. No. 5,201,742 A, a device is presented that serves for precise orientation of a minimally invasive instrument, in such a manner that the orientation takes place about a fixed point, by means of circle arc guide, in the center of which the point of rotation of the instrument is situated, and on which the instrument can be manually swiveled and fixed in place when the desired position has been reached.
A technical solution for tracing is presented in accordance with DE 3545008 A1. An arc guide that comprises a quarter circle is connected with a rotary joint in such a manner that the axis of rotation and the center of the axis of rotation intersect, and a tool can be freely swiveled about this intersection point, in the region of a hemisphere.
All of the technical solutions having arc guides have specific disadvantages inherent in them. Arc guide elements are heavy, cost-intensive precision components, and they take up their entire movement range as a collision space. Of course, the movement range is limited.
A robot wrist for swiveling a tool about a fixed point is indicated in DE 3211688 A1, for which purpose a so-called double parallel guide is used. Again, comparatively many elements and joints are required. Low rigidity, particularly perpendicular to the movement plane of the parallelogram guide, is the result. The great number of rotary joints in the device makes its mobility without play more difficult. The movement range is limited to approximately 120°, because of the so-called dead points of the mechanism.
A further development of this principle is described in Yang, C. H., Rauchfuss, J. W.: A new Zero-Dimension Robot Wrist: Design and Accessibility Analysis, The International Journal of Robotics Research, Vol. 20, No. 2, February 2001, pp. 163-173. Two parallel crank mechanisms disposed on top of or inside one another eliminate the limitation of the swiveling range, and theoretically allow swiveling of the tool about 360°. However, all of the other disadvantages of parallel crank mechanisms remain.